Transformer oils



Patented Mar. 16, 1954 TRANSFORMER OILS William T. Stewart, Berkeley, Charles D. Newnan, San Pablo, and Neal W. Furby, Berkeley, Calif., assignors to California Research Corporation, San Francisco, Calif., a corporation of Delaware No Drawing. Application April 29, 1950, Serial No. 159,142

12 Claims. 1

This invention relates to the stabilization of lubricating oil compositions intended for use in the service of transformer oils, turbine oils and the like. More particularly, this invention pertains to the use of so-called synthetic lubricating oil compositions as transformer oils, wherein the anti-oxidation characteristics of the anti-oxidant present in the composition (e. g., selenium compounds) have been enhanced by the presence of hydroxy anthraquinone compounds (e. g., quinizarin) This application is a continuation-in-part of the Stewart et al. application Serial No. 109,426 filed August 9, 1949.

For a number of years, it has been the general practice to use moderately treated mineral oils as transformer oils. However, these moderately treated oils gradually deteriorate in service. The effectiveness of transformer oils as insulating oils is materially reduced by oxidation products (i. e., the acid products) formed. These acid products also gradually attack the insulation on the wires of the transformer system,

leaving the Wires partially exposed to the oil, which oil then serves as a transmitter of current instead of an inhibitor of current. In the turbine oils the oxidation products (i. e., the acid sludges) corrode the bearings and other parts of the turbine system and clog the oil lines, etc.

It is a tremendous advantage in transformer, turbine, and like systems to use oils of sumcient oxidation stability to permit their use over long periods of time without being changed. [Not only is it desirable to have transformer oils and the like highly resistant to oxidation, but it is also a desired feature of the transformer oils and the like that the viscosity index be high that is, that only small changes in viscosity occur with large changes in temperature. Thus, in order to obtain oils of high viscosity index, it is advantageous in some instances to use synthetic oils which are prepared especially to resist changes in viscosity with changes in temperature.

In attempting to increase the oxidation stability of transformer and turbine oils, known oxidation inhibitors (such as the dialkyl selenides of Denison and Condit Patents Nos. 2,398,414 and 2,398,415) were incorporated therein, and, as expected, the resulting compounded oils were more resistant to oxidation than the base oils containing no inhibitors. However, it was not to be expected that the oxidation stability of the oil thus compounded with oxidation inhibitors could be increased still furtherby adding thereto an agent w'h'ichf' by; its'elf.' .'is.-T not 1 oxidation inhibitor.

It is an outstanding feature of this invention that the oxidation stability of lubricating oils compounded with oxidation inhibitors is materially increased by adding thereto an agent not known as an oxidation inhibitor which agent asserts synergistic effects in combination with the oxidation inhibitors of this invention.

It is a primary object of this invention to produce polyalkylene oxide lubricating oil compositions which are highly resistant to oxidation.

It is another object of this invention to incorporate in polyalkylene oxide oils containing oxidation inhibitors an agent exhibiting a marked synergistic effect on certain oxidation inhibitors.

It is a further object of this invention to produce transformer oils and the ilke which are more resistant to oxidation than those heretofore.

known.

These and other objects may be obtained from the disclosures and the claims noted hereinbelow.

It has been discovered that highly oxidation resistant polyalkylene oxide compositions of lubricating viscosity may be prepared by incorporating hydroxy anthraquinones in said compositions containing oxidation inhibitors, par-- ticularly, selenides.

Synthetic oils of the alkylene oxide type polymer which are used include those exemplified by the alkylene oxide polymers (e. g., propene oxide polymers) and derivatives, including alkylene oxide polymers prepared by polymerizing alkylene oxides, e. g., propylene oxide, in the presence of water or alcohol, e. g., ethyl alcohol, and esters of alkylene oxide type polymers, e. g., acetylated propene oxide polymers prepared by acetylating propene oxide polymers containing hydroxyl groups.

The hydroxy anthraquinones of this invention are anthraquinones containing at least one hydroxyl group on the ring, such as exemplified by l-hydroxy anthraquinone, alizarin (1,2-dihydroxy-anthraquinone), quinizarin (1,4-dihydroxy anthraquinone), 1,5 dihydroxyanthraquinone and 1,8-dihydroxy anthraquinone. It is preferred to use dihydroxy anthraquinones, particularly, quinizarin.

Oxidation inhibitors which are contemplated by this invention to be used'in viscous oil compositions in combination with hydroxy anthraquinones include selenides. The particular selenides of the present invention may be represented by the formula:

hydrocarbonaceous organo groups connected to selenium through an aliphatic carbon atom, at least R, and preferably also R1 and R2, contain at least carbon atoms, preferably 12 to 3() carbon atoms, and M represents a cationic salt-forming radical, such as a metal atom. Thus, sele nides embrace di-organo monoand di-selenides, selenomercaptans (organo hydroselenides) and selenomercaptides (metallo organo selenides). Preferred are the di-organo selenides (i. e., R-SenR", where 12:1 .or 2 and R and R are like or unlike aliphatic radicals each of at least 10 carbon atoms); of these, the monoselenides are ordinarily preferred.

Suitable organo groups, which are preferably hydrocarbon groups, include alkyl groups, such as decyl, lauryl, cetyl, etc., alkylated cyclo aliphatic radicals, such as ethyl cyclo'hexyl, dimethyl cyclohexyl, etc., alkylated aralkyl radicals, such as cetylbenzyl, butylbenzyl, etc., and the aliphatic radicals derived from halogenated mixtures of hydrocarbons such as chlorinated naphtha, chlorinated kerosene, chlorinated parafiin wax, etc. The aliphatic groups may contain non-hydrocarbonsubstituents such as chlorine, bromine, hydroxyl and amino so long as their essentially hydrocarbon character remains substantially unchanged. Of these various types of organo groups, the alkyl radicals are prefer-red and of these, the dodecyl group is especially preferred.

The cationic salt-forming radical may be metals, such as sodium, calcium, barium, zinc, -potassium, lithium, strontium, aluminum, lead, thallium, etc., or the ammonium radical. Preferably, the metals are the polyvalent metals, especially those of groups 11b, IV and VIII of the periodic table.

The following specific examples of selenides will further illustrate the selenium compounds of the present invention: diallryl selenides, such ,as octyl decyl monoselenide, dilauryl monoselenide, dieicosyl monoseleni-de, dialkyl 'diselenides, such as didecyl diselen-ide, d-idodecyl diselenide (clilauryl diselenide), diheptadecyl ,diselenide, dieicosyl diselenide, selenomercaptans, such as lauryl selenomercaptan, ,cetyl selenomercaptan, octadecyl selenomercaptan, parafiin wax selenomercaptan, etc,, and the corresponding sodium, calcium, barium, zinc, cadmium and lead salts of such selenomercaptans.

The oxidation inhibitors (1. .e., the organic selenium compounds) which are present in the lubricating oil composition may 'be present in amounts from about '0.0001% to abput 5% by weight of the final composition, that is, an amount sufficient .to increase the resistance of the lubricating oil composition to oxidation. It is preferred to use from about 0.1% to about 2.0%

The hydroxy anthraquinones of this invention (e. g., quinizarin) may be present in the f nal mineral oil composition in amounts from about to abou 1.4 y we ght cf the final composition It is p f red an amount suffic ent to nhance the .cxidati n-inhibit ns h ra eristics of he or ani selenium comig uid. r ferably from about 0.02% to a ut 'I'he organic selenium compound can be replaced in part by alkylated phenol oxidation inhibitors, such as 2,6-di-tertiary butyli-methyl phenol, to procure a long life tor the compounded 0.1L. de irable since it provides a way 0! cutting dcwn the am mt c xp nsiv sel nide without reducing the long life as obtainable with selenides alone. Thus, a hydroxy anthraquinone (e. g., quinizarin) may be added to a lubricating oil containing an alkylated phenol oxidation inhibitor (e. g., 2,6-di-tertiary butyl-4- methyl phenol) and .a selenide cxidajtion inhibitor (e. g., dilauryl monoselenide) to obtain a long life for the compounded oil.

A remarkable feature of this invention is the wholly unexpected, greatly enhanced synergistic efiects which are obtained between lubricating oil oxidation inhibitors (e. g., organic selenium compounds) and the hydroxy anthraquinones ,(e. g., quinizarin) Nowhere would any one expect to find such synergistic effects as disclosed herein by the addition of a hydroxy anthraquinone as a secondary agent to a lubricating oil composition containing additives which are known to inhibit oxidation, particularly to find its anti-oxidation properties enhanced so tremendously by the addition of a secondary agent which in itself has relatively no effect in inhibiting oxidation in a lubricating oil. Obviously, it is not merely an additive effect which is obtained between the combinations of the known oxidation inhibitor in the lubricating -oil and the hydroxy anthraquinones because the 'hydroxy anthraq-uinones in themselves are practically ineffective in inhibiting the oxidation in the lubricating oil composition.

In the table hereinbelow, data are presented to show the synergistic effects obtained by testing the compositions of additives in a -pol-ya1kylene oxide lubricating oil under severe conditions. In order to test efiectivel-y the compositions of this invention, a more drastic test was devised than is normally used in evaluating transformer oils and the like. This test has been cal-led the California Research Transformer Oil Stability Test. 'The test is run as follows:

A 300 gram sample to 'be tested is placed in a glass tube which is set in an oil bath at 250 F. Oxidation catalysts, i. e., 112% square centimeters of medium silicon transformer iron {such as USS Trancor '72) and 450 square centimeters of No. 14 gauge electrolytic copper wire are inserted in the tube. Dxygen is bubbled through the test sample at the rate of 3 liters per hour until the test sample has an acid number of 1.0 (milligrams of 'KOH per gram sample of oil). The number of hours required for the sample to show an acid number of 1.0 is known as the Test Life of the sample.

The data presented in Table I will serve to illustrate the natureof the results that were obtained in accordance with the pres nt invention. The base oil sed in c tainine the data of Tabl I is described as an iso-octyl alcohol-initiated polypropene oxide acetate, haying a viscosity of 88 SSU at F. The vfollowing equations and Example I exemplify the manner in which the iso-octyl alcohol-initiated polypropene oxide acetate was obtained:

( E01 I BJQE /QLHI 3L0 CaHsBOADIH whe ein and 28; rep esen 'hxd 'ocarhcn radii EXAMPLE I' A mixture of 0.75 part by weight of metallic sodium and 32.1 parts by weight of 2-ethy1 hexanol was heated with agitation to ZOO-220 F. while sweeping out the hydrogen evolved with nitrogen. After hydrogen evolution ceased, the vessel and contents were heated to 240 F. Propene oxide having a water content of less than 0.1% was added until the pressure in the vessel was 40 p. s. 1. (pounds per square inch). As the polymerization progressed, additional propene oxide was added to maintain the pressure at 40 p. s. i. while holding the temperature at 240 F. until 115 parts of propene oxide had been added. Thereafter the reaction mixture was stirred for an additional hour. 15 parts by weight ofacetic anhydride were then added and the reaction mixture was heated at 300 F. for 4 hours, after which time the impurities and unreacted ingredients were removed by stripping at a pressure of about 25 mm. of mercury with a pot temperature of about 300 F. The residue was then filtered.

In the specific base oil used in the examples of Table I, the mol ratio of alcohol, to propene oxide was 1 to 8. This synthetic oil is also termed a polypropene glycol octyl ether acetate.

Table I "Test Life" on (Hrs) Base 011 Less than 20. Base Oil+0.05% Quinizarin H- Do. Base 0il+2.0% Dilauryl selenide Base Oil+2.0%Dilauryl Selenide+0.05% Quinizarln| The hydroxy anthraquinones may also be used in oils containing other groups of additives in addition to anti-oxidants. For example, in addition to the above-noted compounds, these lubricating oils may contain other agents, such as pour point depressants, oiliness agents, extreme pressure agents, blooming agents, compounds for enhancing the viscosity index of the synthetic oils, grease-forming agents, peptizing agents, etc.

As used herein, the terms "substantially hydrocarbonaceous and essentially hydrocarbon refer to groups which are composed almost entirely of only hydrogen and carbon atoms. It is not intended that the hydrogen and carbon atoms are the only atoms present. The terms embrace groups which are composed almost entirely of hydrogen and carbon atoms and the derivatives of these groups. That is, in addition to the hydrogen and carbon atoms, the groups may contain chlorine, bromine, hydroxyl, amino groups,

etc., so long as there are sufiicient hydrogen and carbon atoms present to retain the hydrocarbon character of the groups.

We;: claim:

1. A lubricating oil composition consisting essentially of a major portion of a low molecular an amount from about 0.0001% 6 weightalkylene oxide liquid polymer of lubricat ing viscosity. which polymer is substantially free from groups normally reactive with selenides .and dihydroxyanthraquinones, and a small amount, sufiicient to increase the resistance of the lubri eating oil to oxidation, of a selenide having at least one aliphatic group of at least 10 carbon atoms attached to the selenium atom, to which lubricating oil composition is further added a synergist for the selenide, said synergist being a dihydroxyanthraquinone which is present in the lubricating oil composition in an amount from about 0.0001% to about 1.0%, by weight.

2. A lubricating oil composition consisting essentially of a major portion of a low molecular weight alkylene oxide liquid polymer of lubricating viscosity, which polymer is substantially free from groups normally reactive with selenides and dihydroxyanthraquinones, and a small amount, sufiicient to increase the resistance of the lubricating oil to oxidation, of a selenide represented by the formula wherein R. and R1 are aliphatic groups containing at least 10 carbon atoms, to which lubricating oil composition is further added a synergist for the selenide, said synergist being a dihydroxyanthraquinone which is. present in the lubricating oil composition in an amount from about 0.0001% to about 1.0%, by weight.

3. A lubricating oil composition consisting of a major proportion of an esterified low molecular weight alkylene oxide liquid polymer of lubricating viscosity, which polymer is substantially free from groups normally reactive with selenides and dihydroxyanthraquinones, and from about 0.0001% to about 5%, by weight, of a selenide having at least one aliphatic group of at least 10 carbon atoms attached to the selenium atom, to which lubricating hydrocarbon oil composition is further added a synergist for the selenide, said synergist being a dihydroxyanthraquinone which is present in the lubricating oil composition in to about 1.0%, by weight.

4. A lubricating oil composition consisting of a major proporition of a low molecular weight alkylene oxide liquid polymer of lubricating viscosity, which polymer is substantially free from groups normally reactive with selenides and hydroxyanthraquinones, and from about 0.1% to about 2.0%, by weight, of a selenide having at least one aliphatic group of at least 10 carbon atoms attached to the selenium, to which lubricating oil composition is added a synergist for the selenide, said synergist being a dihydroxyanthraquinone, and being present in the lubrieating oil composition in an amount from about 0.02% to about 0.1%, by weight.

5. A lubricating oil composition consisting essentially of a major portion of a low molecular weight alkylene oxide liquid polymer of lubricating viscosity, which polymer is substantially free from groups normally reactive with selenides and dihydroxyanthraquinones, and a small amount, sufiicient to increase the resistance of the lubricating oil to oxidation, of a selenide represented by the formula wherein R and R1 are aliphatic groups containing at least 10 carbon atoms, to which lubricating oil composition is further added a synergist for the selenide, said synergist being a dihydroxyantm-aquinone which lie *present. an rthe lubricating oil composition in an amount rom abnut O-.OOO1'% to about 150% A lubricating oll composition consisting ressentially o: a major portion :of Ta. low molecular weight aikylene'oxide liquid polymer of Z'lubricating viscosity, which molymer is substantiallyifree from groups-normally reaottve with selenides and c'iihydroxyanfihraquinones, and a small amoimt, suflicient its increase the resistance 'of the lubricating oil :to oxidation. of :a 'selenide represented by the iormula R-Se-M wherein *R an aliphatic group containing at least :10 carbon atoms and M is a cationic salt- :forzning radical, to which lubricating oil com-position is further added a :synerg-ist for the selenide, said rsynergist being a dihydroxyanthraquinone which is present in the lubricating oil comgpo'sition in an amount from about 0.0001% to about 1.0%, by weight.

'7. A low molecular weight alkylene oxide liquid polymer of lubricating viscosity, which polymer is -.substantially free from groups normally reactive with 'selenides and dihydroxyanthraqui- 'nones, to which is added :a small amount, 'sufficient to increase the resistance of said 'alkylene oxide liquid polymer to oxidation, of a 's'elenid'e having at least one aliphatic group of at least 10 carbon atoms attached to the selenium atom, to which composition is further added a synergist for the selenide, said .synergist being a dihydroxyanthraquinone which is present in the alkylene oxide liquid polymer lubricating composition in an "amount from about 0.130111% to about 1.0%,, by weight.

8. 'The lubricating oil composition of claim '4, wherein the low molecular weight alkylene oxide liquid polymer of lubricating viscosity is an alcohol initiated and esterified polymerization prodnot of low molecular weight alkylene oxide.

'9. The lubricating oil composition of claim '4, wherein the low molecular weight alkylene oxide liquid .polymer of lubricating viscosity is an octyl alcohol initiated polypropen'e oxide acetate.

10. The lubricating 'oil composition of claim 4, wherein the 's'elenide is a 'dialkyl monoselenide.

'11. The lubricating oil composition of claim '4, wherein the .selenide is diiaury'l monoselenide.

12. Thelubricating oil composition of claim 4, wherein the hydroxy anthraquinone is quinizarin.

WILLIAM 'I. STEWART. CHARLES D. NEWNAN. NEAL W. FURBY.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,016,648 Orelup Oct. 8, 1935 2,214,443 Varteressian Sept. 10, 1940 2,398,415 Denison, Jr., et al. Apr. 16, 1946 2.434378 Zisman Jan. 27, 1948 2,497,097 Roberts Feb. 14, 1950 

1. A LUBRICATING OIL COMPOSITION ESSENTIALLY OF A MAJOR PORTION OF A LOW MOLECULAR WEIGHT ALKYLENE OXIDE LIQUID POLYMER OF LUBRICATING VISCOSITY, WHICH POLYMER IS SUBSTANTIALLY FREE FROM GROUPS NORMALLY REACTIVE WITH SELENIDES AND DIHYDROXYANTHRAQUINONES, AND A SMALL AMOUNT, SUFFICIENT TO INCREASE THE RESISTANCE OF THE LUBRICATING OIL TO OXIDATION, OF A SELENIDE HAVING AT LEAST ONE ALIPHATIC GROUP OF AT LEAST 10 CARBON ATOMS ATTACHED TO THE SELENIUM ATOM, TO WHICH LUBRICATING OIL COMPOSITION IS FURTHER ADDED A SYNERGIST FOR THE SELENIDE, SAID SYNERGIST BEING A DIHYDROXYANTHRAQUINONE WHICH IS PRESENT IN THE LUBRICATING OIL COMPOSITION IN AN AMOUNT FROM ABOUT 0.0001% TO ABOUT 1.0%, BY WEIGHT. 